The present invention relates to a stethoscope and more particularly to a combination stethoscope having both an acoustic mode and an electronic mode.
The stethoscope has been used for auscultation since its invention in the early nineteenth century. The need for and efforts exerted to develop improved stethoscopes is evidenced at least in part by the many patents which have issued directed to various improvements therein. One direction that improvement has taken has been toward stethoscopes having electronic means for amplifying the sounds produced in the body.
Thus, one finds patents such as Dahl U.S. Pat. No. 3,087,016 which is directed to a combination acoustic and electronic stethoscope consisting of a chestpiece with diaphragm, a hollow handle attached to the chestpiece, and a tube, one end of which is bifurcated for engagement with an operator's ears. Behind the diaphragm is a microphone located in a chamber having an air passage joining the chamber through a hollow bolt to the cavity of the handle. In the air passage is a valve which, on closing, both blocks the air passage and also activates the electronics for operation in the electronic mode. The speaker and batteries are located in the handle cavity. This stethoscope has the disadvantage that when operated in the acoustic mode, sound must travel through the microphone and through the speaker system resulting in attenuation of many frequencies.
Cefaly et al U.S. Pat. No. 3,247,324 discloses a combination acoustic and electronic stethoscope which avoids the attenuation of frequencies inherent in the stethoscope of Dahl by placing just below the position where the tube from a standard chestpiece is bifurcated a housing containing two chambers, one connected to the tube from the chestpiece, the other connected to the tube just below the bifurcation. The chestpiece-chamber has an opening to a microphone and the other chamber has an opening to a speaker. Connecting the two chambers is a tube providing an unimpeded air system from the diaphragm of the chestpiece to the ears of the operator. In this connecting tube is a valve, the operation of which closes the air system and actuates the electronics providing amplification of sound picked up by the microphone and put out by the speaker. Such a stethoscope, though avoiding attenuation of sound, is clumsy and requires two hands to operate.
Keesee U.S. Pat. No. 3,539,724 relates to a combination electronic and acoustic stethoscope which permits selection of the mode of operation by a valve means which, in one position, establishes a passageway directly to the earpieces and in a second position establishes a pathway through an electronic amplifier. Although a stethoscope having such capabilities is desirable and would appear to be technologically feasible, the stethoscope shown and described in the patent would be extremely cumbersome to use.